Anti-skinning agents having a mixture of organic compounds and coating compositions containing them

ABSTRACT

The invention relates to anti-skinning agents containing mixtures of organic compounds (combinations of additives), whereby the organic compounds are selected from the groups of organic hydroxylamines, and β-dicarbonyl compounds and/or selected derivatives of formic acid and also relates to compositions containing them, especially oxidatively drying paints or coating compositions.

FIELD OF THE INVENTION

[0001] The invention relates to anti-skinning agents containing mixturesof organic compounds (combinations of additives) and coatingcompositions containing them. The organic compounds are selected fromthe groups of organic hydroxylamines, and β-dicarbonyl compounds and/orselected derivatives of formic acid. The invention further relates tocompositions containing these anti-skinning agents, like coatingcompositions such as oxidatively drying paints.

BACKGROUND OF THE INVENTION

[0002] Colorless and pigmented oxidatively drying paints and coatingsbased on oxidatively drying oils, alkyd resins, epoxy esters and otheroxidatively drying refined oils are known. These oils and binderscrosslink oxidatively under the influence of oxygen (preferablyatmospheric oxygen) by means of the addition of driers, such as metalcarboxylates of transition metals. If this crosslinking takes placebefore the product is actually used, they can form a solid binder film,a skin, on the surface when stored in open or closed containers. This ishighly undesirable and should therefore be avoided since it makes thepaint more difficult to work with, and commonly interferes with theuniform distribution of the driers. The accumulation of the driers inthe paint skin that forms can lead to considerable delays in the dryingof the paint when it is applied.

[0003] Skinning in the paint film after application is alsodisadvantageous. Excessively rapid drying of the surface of the paintprevents the lower film layers from drying evenly because they areshielded from oxygen, which is prevented from sufficiently penetratinginto and dispersing within the paint film. This can lead among otherthings to flow problems in the paint film, adhesion problems, orinsufficiently hard films.

[0004] It is known to add organic substances to the paint that inhibitthe reaction of the drier metal with (atmospheric) oxygen by binding theoxygen or by complexing of the drier metal. Formulations of knowncompounds that are suitable for this purpose can be found e.g. in H.Kittel “Lehrbuch der Lacke und Beschichtungen”, Colomb Verlag 1976; J.Bieleman “Lackadditive” Wiley VCH 1998 or Römpp Lexikon “Lacke undDruckfarben”, Thieme Verlag 1998.

[0005] Furthermore, DE-A 3 418 988 describes the use of aliphaticα-hydroxy ketones as anti-skinning agents, and DE-A 1 519 103 disclosesN,N-dialkylated hydroxylamines for this purpose. Because of their lowvolatility, however, these agents can lead to severe delays in dryingand often also to reduced film hardness values, so that their possibleapplications are limited. They have not been able to gain acceptance asanti-skinning agents.

[0006] EP-A 0 903 380 describes the use of α-keto-functionalisedcarboxylic acids and dicarboxylic acids and of derivatives thereof,optionally in combination with diketo compounds, as anti-skinningagents. A disadvantageous property of such products lies in theirlimited stability and hence restricted storage life.

[0007] Finally, pyrazole or imidazole derivatives, optionally incombination with aliphatic diketones, in particular acetylacetone, arerecommended for this purpose in WO 00/11090. However, the cited aromaticamines can cause severe discoloration in the coating composition andalso in the applied paint film and likewise give rise to severe delaysin drying.

[0008] Oximes (in particular butanone oxime) or suitable phenoliccompounds are mostly used today as anti-skinning agents in industry. Thephenolic anti-skinning agents display a significant delay in surfacedrying, however, such that alone they are only suitable for certaincoating compositions. Oximes such as e.g. methyl ethyl ketoxime orbutyraldoxime, on the other hand, display only slight delays in surfacedrying due to their volatility. The most significant disadvantage of theoximes, which are widely used today, lies in their toxicity. Inlong-term inhalation studies on rats and mice, for example, an increasedoccurrence of liver tumors was observed after exposure to butanoneoxime, as a result of which the German MAK committee has classified thesubstance as a category III A 2 carcinogen (MAK list 1997) [MAK=maximumallowable concentration in the workplace]. As a consequence of this,users have to observe elaborate personal protection precautions whenworking with paints containing oximes as anti-skinning agents.

[0009] It is an object of the present invention to develop organiccompounds which prevent skinning in paints and coating compositions overan extended period and display only a slight delay in surface drying.Furthermore, the film hardness values obtained in the resulting films orcoatings should not be negatively influenced and no discoloration shouldbe caused. The products should display no disadvantageous toxicologicalproperties.

[0010] It is another object of the invention that the organic compoundscan be incorporated into many different oxidatively drying paints andcoatings and by virtue of their physical properties can be usedstraight-forwardly and for many purposes in corresponding coatingcompositions.

[0011] Surprisingly it was found that these requirements could beachieved by the use of mixtures containing the organic compoundsdescribed below. In particular, the above-mentioned disadvantages of thespecified hydroxylamines as anti-skinning agents could also be avoidedby combining such substances with the additional compounds describedbelow, and hence products that better satisfy requirements asanti-skinning agents are obtained.

[0012] In air-drying paints the mixtures according to the invention aresuitable for preventing undesirable skinning, for improving the completedrying of paint films after application and for reducing the tendency ofthe applied paint film to discolor.

SUMMARY OF THE INVENTION

[0013] The invention relates to an anti-skinning agent containing

[0014] a) an organic compound of formula (I)

[0015] where

[0016] R¹ and R² mutually independently represent hydrogen, a linear orbranched, saturated or unsaturated C₁-C₂₀ aliphatic radical, which canoptionally be mono- or polysubstituted, or a C₆-C₁₂ aryl radical, aC₇-C₁₄ araliphatic radical or a C₅-C₇ cycloaliphatic radical, and eitheror both of

[0017] b) an organic compound of formula (II)

[0018] where

[0019] R³ represents hydrogen, a hydroxyl radical, a substituted orunsubstituted, saturated or unsaturated C₁-C₁₉ aliphatic radical, aC₁-C₇ alkoxy radical, or an amine radical —NR⁷R⁸,

[0020] R⁴ represents hydrogen, hydroxyl radical, a substituted orunsubstituted, saturated or unsaturated C₁-C₁₉ aliphatic radical, aC₁-C₇ alkoxy radical, or an amine radical —NR⁹R¹⁰,

[0021] R⁷ and R⁸ mutually independently represent hydrogen or a C₁-C₆aliphatic radical,

[0022] R⁹ and R¹⁰ mutually independently hydrogen or a C₁-C₆ aliphaticradical, and

[0023] c) an organic compound of formula (III)

[0024] where

[0025] R⁵ represents hydrogen, a hydroxyl radical or a C₁-C₇ alkoxyradical and

[0026] R⁶ represents hydrogen or an amine radical —NR¹¹R¹²,

[0027] R¹¹ and R¹² mutually independently represent hydrogen,substituted or unsubstituted C₁-C₆ aliphatic radical, or substituted orunsubstituted C₅-C₇ cycloaliphatic radical, or amine radical —NR¹R²

[0028] with the proviso that R⁵ and R⁶ are not simultaneously hydrogen.

[0029] The invention also relates to compositions of matter containingthese anti-skinning agents.

DETAILED DESCRIPTION OF THE INVENTION

[0030] For the purposes of the invention mixtures of organic compoundsof formulae (I) to (III) are used alone or as solutions or dispersionsor emulsions in water and/or organic solvents. Suitable organic solventsinclude all conventional solvents, such as aromatics, white spirits,ketones, alcohols, ethers and fatty acid esters.

[0031] For the use according to the invention the organic compounds offormulae (I) to (III) can be used in a broad range of mixtures with oneanother. They are preferably used in the ratio (I):(II) or (III)=0.1:10to 10:0.1 parts. In a mixture consisting of all three components, eachof the components can mutually independently preferably be used in theratio 0.1 to 10 to each of the other components used. They can be usedin pure form or in aqueous solution or aqueous dispersion or emulsion orin the form of solutions in organic solvents, whereby aqueous in thiscontext is intended to mean that water is either the sole solvent or isadded in a quantity of over 50 wt. % relative to the solvent blendtogether with conventional organic solvents (e.g. alcohols).

[0032] The amount of anti-skinning agents primarily depends on thecontent of binder and drier used in the particular coating composition.As a general rule between 0.001 and 2.0 wt. % of mixtures of compoundsaccording to formulae (I) to (III) should be added. Preferred amounts tobe used are 0.01 to 0.5 wt. %, relative in each case to the overallrecipe of the coating composition. The amounts can also depend on thetype of binder and the pigments used. Thus in special systems therelative amount of additive to be used can also be greater than 2.0 wt.% (relative to the overall recipe).

[0033] It is an advantage of the anti-skinning agent of the presentinvention that it reliably prevent skinning in a wide range of bindersand when used with various driers but does not unfavorably influenceother drying properties of the paint.

[0034] The invention is further illustrated but is not intended to belimited by the following examples in which all parts and percentages areby weight unless otherwise specified.

EXAMPLES

[0035] The following embodiments of the mixtures of organic compounds offormulae (I) to (III) that are suitable for use according to theinvention as anti-skinning agents are cited by way of example:

[0036] a) 19% diethyl hydroxylamine, 22% diethyl formamide, 59% water;

[0037] b) 19% diethyl hydroxylamine, 22% diethyl formamide, 59% ethanol;

[0038] c) 15% diethyl hydroxylamine, 9% 2,4-pentane dione, 60% ethanol,16% water;

[0039] d) 19% diethyl hydroxylamine, 17.5% N-methyl acetoacetamide,63.5% ethanol;

[0040] e) 10% diethyl hydroxylamine, 9% hydrazine ethyl carboxylate,79.5% ethanol, 1.5% water;

[0041] f) 25% dibenzyl hydroxylamine, 15% N-methyl acetoacetamide, 10%ethanol, 50% acetone;

[0042] g) 23% dibenzyl hydroxylamine, 10% diethyl formamide, 10%ethanol, 57% acetone;

[0043] h) 10% diethyl hydroxylamine, 9% malonic acid, 10% diethylformamide, 60% ethanol, 11% water;

[0044] i) 10% diethyl hydroxylamine, 9% ethyl formiate, 50% ethanol, 31%water;

[0045] j) 10% diethyl hydroxylamine, 10% ethyl acetoacetate, 78% water;

[0046] k) 10% diethyl hydroxylamine, 9% dimethyl malonate, 60% ethanol,21% water;

[0047] l) 10% diethyl hydroxylamine, 9% malonic acid, 50% ethanol, 31%water;

[0048] m) 20% hydroxylamine, 15% N-methyl acetoacetamide, 30% ethanol,35% water;

[0049] n) 24% hydroxylamine, 11% hydrazine ethyl carboxylate, 25%ethanol, 40% water.

[0050] Examples of the Use of Anti-Skinning Agents According to theInvention

[0051] 1. 0.15 g of a cobalt-containing drier (trade name Octa-SoligenCobalt 6 from Borchers GmbH, contains 6 wt. % Co), 0.33 g of azirconium-containing drier (trade name Octa-Soligen Zirkon 18 fromBorchers GmbH, contains 18 wt. % Zr) and 0.18 g of a calcium-containingdrier (trade name Octa-Soligen Calcium 4 from Borchers GmbH, contains 4wt. % calcium) were added to a coating composition consisting of 25.0 gof a long-oil, high-gloss white alkyd resin topcoat (binder solidscontent 68 wt. %). 0.018 g of the mixture listed under a) was added tothe formulation and the time taken for a skin to form on the surface ofa closed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for 33 days in this case. By way of comparison, theskinning time for a sample without anti-skinning additive determinedunder identical conditions was 5 days, that for a sample containing aconventional, suitable amount of butanone oxime (0.12 g) was 18 days.The color co-ordinate b* of a corresponding paint film with a 100 μm wetfilm thickness (according to CIELAB, corresponding to DIN 6174)determined after a storage period of 1 week resulted in a value when themixture according to the invention was used that was 0.7463 points lowerthan the tristimulus value of the sample containing butanone oxime,determined under identical conditions, as a result of which a reducedyellowing of the film was indicated.

[0052] 2. 0.38 g of a cobalt-containing mixed drier (trade nameOcta-Soligen Trockner 203 from Borchers GmbH, contains 1.2 wt. % Co, 3.2wt. % zinc and 7.2 wt. % barium) was added to a coating compositionconsisting of 25.0 g of a high-gloss white alkyd resin topcoat (bindersolids content 36.9 wt. %). 0.046 g of the mixture listed under c) wasadded to the formulation and the time taken for a skin to form on thesurface of a closed 125 ml PE beaker filled to approx. ¼ wasestablished. Skinning was prevented for more than 27 days in this case.By way of comparison, the skinning time for a sample withoutanti-skinning additive determined under identical conditions was 2 daysand that for a sample containing a conventional, suitable amount ofbutanone oxime (0.041 g) was 10 days. The gloss of the paint film(according to DIN 67530) determined after a storage period of 1 week wasdetermined as 85.9 points (measured at 200) and 92.8 points (measured at60°) when the mixture according to the invention was used. By way ofcomparison, the gloss of the paint film from the sample withoutanti-skinning additive determined under identical conditions was 81.6points (measured at 20°) and 88.5 points (measured at 60°), that of thefilm from the sample containing butanone oxime was 82.1 and 89.9 points(at 20° and 60° respectively). The color co-ordinate b* of acorresponding paint film with a 100 μm wet film thickness (according toCIELAB, corresponding to DIN 6174) determined after a storage period of1 week resulted in a value when the mixture according to the inventionwas used that was 0.300 points lower than the tristimulus value of thesample containing butanone oxime, determined under identical conditions,as a result of which a reduced yellowing of the film was indicated.

[0053] 3. 0.10 g of a cobalt-containing drier (trade name Octa-SoligenCobalt 6 from Borchers GmbH, contains 6 wt. % Co) and 0.4 g of acalcium-containing drier (trade name Octa-Soligen Calcium 4 fromBorchers GmbH, contains 4 wt. % calcium) were added to a coatingcomposition consisting of 30.0 g of a long-oil alkyd resin (trade nameAlkydal U 601 from Bayer AG) and 2.2 g white spirit D 60. 0.005 g of themixture listed under d) was added to the formulation and the time takenfor a skin to form on the surface of a closed 125 ml PE beaker filled toapprox. ¼ was established. Skinning was prevented for more than 50 daysin this case. By way of comparison, the skinning time for a samplewithout anti-skinning additive determined under identical conditions was6 days, the skinning time for a sample containing a conventional,suitable amount (0.05 g) of butanone oxime was 16 days and that for asample containing an identical amount (0.001 g) of diethyl hydroxylaminein the same solvent was 7 days. The König pendulum hardness (determinedaccording to DIN 53 157, 100 μm wet film thickness) of a paint film towhich the mixture according to the invention had been added was 97seconds after a storage period of 1 week. By way of comparison, thependulum hardness of the paint film from the sample withoutanti-skinning additive determined under identical conditions was 96seconds, that of the film from the sample containing butanone oxime waslikewise 97 seconds and that of the film from the sample containingdiethyl hydroxylamine was 93 seconds, in each case after a storageperiod of 1 week.

[0054] 4. 0.40 g of a cobalt-containing mixed drier (trade nameOcta-Soligen Trockner 203 from Borchers GmbH, contains 1.2 wt. % Co, 3.2wt. % zinc and 7.2 wt. % barium) was added to a coating compositionconsisting of 30.0 g of a high-gloss white alkyd resin topcoat (bindersolids content 36.9 wt. %). 0.005 g of the mixture listed under b) wasadded to the formulation and the time taken for a skin to form on thesurface of a closed 125 ml PE beaker filled to approx. ¼ wasestablished. Skinning was prevented for 42 days in this case. By way ofcomparison, the skinning time for a sample without anti-skinning agentdetermined under identical conditions was 8 days, the skinning time fora sample containing a conventional, suitable amount (0.05 g) of butanoneoxime was 21 days and that for a sample containing an identical amount(0.001 g) of diethyl hydroxylamine in the same solvent was likewise 21days. The drying time of a corresponding paint film (100 μm wet filmthickness) from the mixture according to the invention was 12 h (scratchdrying according to test specification 100-94 from Borchers GmbH). Thedrying time of a sample without anti-skinning additive determined underidentical conditions was 10 h 30 min., that of the sample containingbutanone oxime was determined as 10 h. The drying time of the paint filmfrom the sample containing diethyl hydroxylamine was 14 h. The colorco-ordinate b* of a corresponding paint film with a 100 μm wet filmthickness (according to CIELAB, corresponding to DIN 6174) determinedafter a storage period of 1 week was 2.2754 when the mixture accordingto the invention was used. The tristimulus values for the sampleswithout anti-skinning agent and with an identical amount (0.001 g) ofdiethyl hydroxylamine in the same solvent determined under identicalconditions were 2.4214 and 2.4434 units respectively, as a result ofwhich a reduced yellowing of the coating composition containing themixture according to the invention was indicated.

[0055] 5. 0.10 g of a cobalt-containing drier (trade name Octa-SoligenCobalt 6 from Borchers GmbH, contains 6 wt. % Co) and 0.4 g of acalcium-containing drier (trade name Octa-Soligen Calcium 4 fromBorchers GmbH, contains 4 wt. % calcium) were added to a coatingcomposition consisting of 30.0 g of a long-oil alkyd resin (trade nameAlkydal U 601 from Bayer AG) and 2.2 g white spirit D 60. 0.023 g of themixture listed under h) was added to the formulation and the time takenfor a skin to form on the surface of a closed 125 ml PE beaker filled toapprox. ¼ was established. Skinning was prevented for 22 days in thiscase. By way of comparison, the skinning time for a sample withoutanti-skinning additive determined under identical conditions was 3 daysand that for a sample containing a conventional, suitable amount ofbutanone oxime (0.05 g) was 10 days. The König pendulum hardness(determined according to DIN 53 157, 100 μm wet film thickness) of apaint film to which the mixture according to the invention had beenadded was 75 seconds after a storage period of 1 week. By way ofcomparison, the pendulum hardness of the paint film from the samplewithout anti-skinning additive determined under identical conditions was73 seconds, that of the film from the sample containing butanone oximewas 76 seconds.

[0056] 6. 0.18 g of a cobalt-containing drier (trade name Trockner 69from Borchers GmbH, contains 6 wt. % Co and 9 wt. % zirconium) and 0.4 gof a calcium-containing drier (trade name Octa-Soligen Calcium 10 fromBorchers GmbH, contains 10 wt. % calcium) were added to a coatingcomposition consisting of 40.0 g of a long-oil alkyd resin (trade nameAlkydal F 681 from Bayer AG), 4.0 g white spirit D 60, 4.0 g xylene, 1.0g n-butanol. 0.04 g of the mixture listed under e) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for 102 days in this case. By way of comparison, theskinning time for a sample without anti-skinning additive determinedunder identical conditions was 11 days, the skinning time for a samplecontaining a conventional, suitable amount (0.10 g) of butanone oximewas 26 days and that for a sample containing an identical amount (0.004g) of diethyl hydroxylamine in the same solvent blend was likewise 26days. The König pendulum hardness (determined according to DIN 53157,100 μm wet film thickness) of a paint film to which the mixtureaccording to the invention had been added was 41 seconds after a storageperiod of 1 week. By way of comparison, the pendulum hardness of thepaint film from the sample without anti-skinning additive determinedunder identical conditions was 29 seconds, that of the film from thesample containing butanone oxime was 32 seconds and that of the filmfrom the sample containing diethyl hydroxylamine was 37 seconds, in eachcase after a storage period of 1 week.

[0057] 7. 0.38 g of a cobalt-containing mixed drier (trade nameOcta-Soligen Trockner 203 from Borchers GmbH, contains 1.2 wt. % Co, 3.2wt. % zinc and 7.2 wt. % barium) was added to a coating compositionconsisting of 25.0 g of a high-gloss white alkyd resin topcoat (bindersolids content 36.9 wt. %). 0.069 g of the mixture listed under i) wasadded to the formulation and the time taken for a skin to form on thesurface of a closed 125 ml PE beaker filled to approx. ¼ wasestablished. Skinning was prevented for more than 21 days in this case.By way of comparison, the skinning time for a sample withoutanti-skinning additive determined under identical conditions was 2 daysand that for a sample containing a conventional, suitable amount ofbutanone oxime (0.041 g) was 10 days. The color co-ordinate b* of acorresponding paint film with a 100 μm wet film thickness (according toCIELAB, corresponding to DIN 6174) determined after a storage period of1 week resulted in a value when the mixture according to the inventionwas used that was 0.166 points lower than the tristimulus value of thesample containing butanone oxime, determined under identical conditions.At the same time a tristimulus value was obtained that was 0.3117 pointslower than the tristimulus value of the sample without anti-skinningagent determined under identical conditions, as a result of which areduced yellowing of the film was indicated. The gloss of the paint film(according to DIN 67530) determined after a storage period of 1 week wasdetermined as 87.8 points (measured at 20°) and 95.6 points (measured at60°) when the mixture according to the invention was used. By way ofcomparison, the gloss of the paint film from the sample withoutanti-skinning additive determined under identical conditions was 81.6points (measured at 20°) and 88.5 points (measured at 60°), that of thefilm from the sample containing butanone oxime was 82.1 and 89.9 points(at 20° and 60° respectively).

[0058] 8. 0.20 g of a cobalt-containing drier (trade name Octa-SoligenCobalt 6 from Borchers GmbH, contains 6 wt. % Co), 0.25 g of azirconium-containing drier (trade name Octa-Soligen Zirkon 18 fromBorchers GmbH, contains 18 wt. % Zr) and 0.46 g of a calcium-containingdrier (trade name Octa-Soligen Calcium 10 from Borchers GmbH, contains10 wt. % calcium) were added to a coating composition consisting of 40.0g of a high-gloss white alkyd resin topcoat (binder solids content 38wt. %). 0.092 g of the mixture listed under k) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for more than 28 days in this case. By way of comparison,the skinning time for a sample without anti-skinning additive determinedunder identical conditions was 5 days and that for a sample containing aconventional, suitable amount of butanone oxime (0.162 g) was 21 days.The König pendulum hardness (determined according to DIN 53157, 100 μmwet film thickness) of a paint film to which the mixture according tothe invention had been added was 79 seconds after a storage period of 1week. By way of comparison, the pendulum hardness of the paint film fromthe sample without anti-skinning additive and that of the film from thesample containing butanone oxime, determined under identical conditions,was in each case 76 seconds after a storage period of 1 week. The colorco-ordinate b* of a corresponding paint film with a 100 μm wet filmthickness (according to CIELAB, corresponding to DIN 6174) determinedafter a storage period of 1 week resulted in a value when the mixtureaccording to the invention was used that was 0.293 points lower than thetristimulus value of the sample containing butanone oxime, determinedunder identical conditions, as a result of which a reduced yellowing ofthe film is indicated when the mixture according to the invention isused.

[0059] 9. 0.20 g of a cobalt-containing drier (trade name Octa-SoligenCobalt 6 from Borchers GmbH, contains 6 wt. % Co), 0.25 g of azirconium-containing drier (trade name Octa-Soligen Zirkon 18 fromBorchers GmbH, contains 18 wt. % Zr) and 0.46 g of a calcium-containingdrier (trade name Octa-Soligen Calcium 10 from Borchers GmbH, contains10 wt. % calcium) were added to a coating composition consisting of 40.0g of a high-gloss white alkyd resin topcoat (binder solids content 38wt. %). 0.092 g of the mixture listed under l) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for more than 28 days in this case. By way of comparison,the skinning time for a sample without anti-skinning additive determinedunder identical conditions was 5 days and that for a sample containing aconventional, suitable amount of butanone oxime (0.162 g) was 21 days.The König pendulum hardness (determined according to DIN 53157, 100 μmwet film thickness) of a paint film to which the mixture according tothe invention had been added was 78 seconds after a storage period of 1week. By way of comparison, the pendulum hardness of the paint film fromthe sample without anti-skinning additive and that of the film from thesample containing butanone oxime, determined under identical conditions,was in each case 76 seconds after a storage period of 1 week. The filmbrightness L of a corresponding paint film with a 100 μm wet filmthickness (according to CIELAB, corresponding to DIN 6174), determinedafter a storage period of 1 week, resulted in a value when the mixtureaccording to the invention was used that was 0.318 points higher thanthe value for the sample containing butanone oxime, determined underidentical conditions, as a result of which a higher film brightness inthe coating containing the mixture according to the invention wasindicated.

[0060] Although the invention has been described in detail in theforegoing for the purpose of illustration, it is to be understood thatsuch detail is solely for that purpose and that variations can be madetherein by those skilled in the art without departing from the spiritand scope of the invention except as it may be limited by the claims.

What is claimed is:
 1. An anti-skinning agent comprising a) an organiccompound of formula (I)

where R¹ and R² mutually independently represent hydrogen, a linear orbranched, saturated or unsaturated C₁-C₂₀ aliphatic radical, which canoptionally be mono- or polysubstituted, or a C₆-C₁₂ aryl radical, aC₇-C₁₄ araliphatic radical or a C₅-C₇ cycloaliphatic radical, and eitheror both of b) an organic compound of formula (II)

where R³ represents hydrogen, a hydroxyl radical, a saturated orunsaturated C₁-C₁₉ aliphatic radical, a C₁-C₇ alkoxy radical, or anamine radical —NR⁷R⁸, R⁴ represents hydrogen, hydroxyl radical, asaturated or unsaturated C₁-C₁₉ aliphatic radical, a C₁-C₇ alkoxyradical, or an amine radical —NR⁹R¹⁰, R⁷ and R⁸ mutually independentlyrepresent hydrogen or a C₁-C₆ aliphatic radical, R⁹ and R¹⁰ mutuallyindependently hydrogen or a C₁-C₆ aliphatic radical, and c) an organiccompound of formula (III)

where R⁵ represents hydrogen, a hydroxyl radical or a C₁-C₇ alkoxyradical and R⁶ represents hydrogen or an amine radical —NR¹¹R¹², R¹¹ andR¹² mutually independently represent hydrogen, C₁-C₆ aliphatic radical,or C₅-C₇ cycloaliphatic radical, or amine radical —NR¹R² with theproviso that R⁵ and R⁶ are not simultaneously hydrogen.
 2. Theanti-skinning agent of claim 1 further comprising water and/or anorganic solvent.
 3. The anti-skinning agent of claim 1 wherein R³represents a substituted C₁-C₁₉ aliphatic radical, a substituted C₁-C₇alkoxy radical, or a substituted amine radical —NR⁷R⁸, and R⁴ represents, a substituted C₁-C₁₉ aliphatic radical, a substituted C₁-C₇ alkoxyradical, or a substituted amine radical —NR⁹R¹⁰, R¹¹ and R¹² mutuallyindependently represent a substituted C₁-C₆ aliphatic radical, or asubstituted C₅-C₇ cycloaliphatic radical, or a substituted amine radical—NR¹R².
 4. The anti-skinning agent of claim 1 wherein the compounds offormula (I) to (III) are in the form of aqueous dispersions oremulsions.
 5. A composition of matter comprising the anti-skinning agentof claim
 1. 6. The composition of matter of claim 5 wherein the amountof anti-skinning agent is between 0.001 and 2.0 wt. % based on thecomposition.
 7. The composition of matter of claim 5 wherein the amountof anti-skinning agent is between 0.01 to 0.5 wt. %, based on thecomposition.
 8. The composition of matter of claim 5 further comprisinga pigment.
 9. The composition of matter of claim 5 wherein thecomposition is a colorless or pigmented paint, a coating, a printing inkbased on oxidatively drying binders, an oxidatively drying paint system,or a spraying agent in a printing ink.